Yeah $1000 is insane. DELL doesn't make the RAM anyway, they're all made by only a few manufacturers, Hynix, Samsung, maybe a few others. You would just need 1x 32GB DDR5-4800 RDIMM. Dell uses part number AC239378.
Maybe just roll with the 1x32gb if it's good enough, but if you can score another stick for $114, that's a pretty good price.
i bought a 32gb dimm on amazon for $99. They say its compatible. I have bad luck on these things.
So a side note on ram. One of the reason Apple has been such a successful company is that they exert enormous pricing power in the Nand memory market. In 2010 they were the largest buyer of Nand memory in the world; I doubt this has changed.